Direct Visualization of Asymmetric Behavior in Supported Lipid Bilayers at the Gel-Fluid Phase Transition

AbstractWe utilize in situ, temperature-dependent atomic force microscopy to examine the gel-fluid phase transition behavior in supported phospholipid bilayers constructed from 1,2-dimyristoyl-sn-glycero-3-phosphocholine, 1,2-dipentadecanoyl-sn-glycero-3-phosphocholine, and 1,2-dipalmitoyl-sn-glycero-3-phosphocholine. The primary gel-fluid phase transition at Tm occurs through development of anisotropic cracks in the gel phase, which develop into the fluid phase. At ∼5°C above Tm, atomic force microscopy studies reveal the presence of a secondary phase transition in all three bilayers studied. The secondary phase transition occurs as a consequence of decoupling between the two leaflets of the bilayer due to enhanced stabilization of the lower leaflet with either the support or the water entrained between the support and the bilayer. Addition of the transmembrane protein gramicidin A or construction of a highly defected gel phase results in elimination of this decoupling and removal of the secondary phase transition

Investigation of Phospholipid Bilayer Interactions With Substrates, Polymers, and Nanoparticles

182 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2007.The last experiments described investigate the ability of water dispersed fullerene aggregates to interact with and disrupt cell membranes. Bilayers composed of both neat zwitterionic lipid headgroups and cationic lipid headgroups were examined to investigate charge interactions between the lipid headgroups and negatively charged fullerene aggregates. Our results indicate that water soluble fullerenes adhere to lipid headgroups and may disrupt cellular functions by either radical generation or cell membrane passivition.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD

Investigation of Phospholipid Bilayer Interactions With Substrates, Polymers, and Nanoparticles

182 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2007.The last experiments described investigate the ability of water dispersed fullerene aggregates to interact with and disrupt cell membranes. Bilayers composed of both neat zwitterionic lipid headgroups and cationic lipid headgroups were examined to investigate charge interactions between the lipid headgroups and negatively charged fullerene aggregates. Our results indicate that water soluble fullerenes adhere to lipid headgroups and may disrupt cellular functions by either radical generation or cell membrane passivition.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD

Poly-L-Lysine-Induced Morphology Changes in Mixed Anionic/Zwitterionic and Neat Zwitterionic-Supported Phospholipid Bilayers

Poly-L-lysine-induced morphological changes in liquid phase supported bilayers consisting of mixed anionic/zwitterionic and neat zwitterionic headgroup phospholipids were studied with atomic force microscopy and epifluorescence microscopy. Results obtained from these studies indicate that poly-L-lysine can induce domains, defects, and aggregate structures on both mixed bilayers and strictly zwitterionic bilayers. The structures formed on liquid phase supported bilayers were observed to be immobile from a timescale of 50 ms to several minutes. We propose that poly-L-lysine of sufficient length interacts with the mica substrate and phospholipids to create the stationary structures noted